The cosmetic treatment of the skin often combines the use of cosmetic preparations with the application of heat. The use of heat provides a number of benefits. It stimulates circulation; it increases the liquidity of the cosmetic preparation, improving its penetration into the skin; it reduces skin stiffness.
Heat may be applied to the skin in a number of ways. The cosmetic preparation itself may be warmed above ambient temperature before being applied to the skin and allowed to cool. Melted paraffin preparations are an example of this technique. Alternatively, the cosmetic preparation is applied to the skin at ambient temperature and hot compresses are applied over the preparation, or the skin is manipulated by means of facial irons or other externally heated sources. A further step in the treatment may involve massage of the warm cosmetic composition on and into the skin surface.
An important part of such treatment is the cosmetic preparation itself. It must possess a number of qualities. The composition must be sufficiently stable that heat does not cause breakdown of ingredients to a non-homogeneous state, yet sufficiently liquid to spread easily under ambient temperature. The composition should readily transport warmth to the skin without requiring extended periods of heating to achieve elevated skin temperature. It should not react to cool the skin below body temperature upon application, thus minimizing the effect of external heat. Its frictional characteristic should not increase upon warming, since this would hamper the ease of manipulation necessary to a massage.
Cosmetic compositions that have been used for thermal treatment of the skin include paraffin, candellila, or ozokerite, carnauba, and other waxes used to formulate "wax masks" which are applied to the skin in a warm liquid state and allowed to cool. However, the pure waxes or wax blends tend to have high frictional effects on the skin. Moreover, they must be premelted and applied while warm. They rapidly cool and set at ambient temperature, allowing no time for manipulation of the skin while the mask is hot.